This invention relates generally to measurement-while-drilling (MWD) systems and, more particularly, to methods and apparatus for securing a measurement while drilling instrument within a drill collar.
It has long been recognized in the exploration for hydrocarbons that obtaining of data from a subsurface instrument during the drilling operation would provide valuable information to the drilling operator. Information such as, for example, weight on bit, rotation rate, inclination and bearing of the borehole, fluid pressure, temperature and certain lithological measurements of the formations are of interest to the drilling operator during the drilling operation. A variety of measurement-while-drilling systems are used to measure such parameters and to transmit the data to the surface of the earth utilizing one of several transmission techniques common in the art.
In a typical embodiment a measurement-while-drilling instrument is mounted within a section of drill collar and affixed within the drill string at a location above the drill bit. The vibrational environment caused by the drilling operation is particularly harmful to electronic and mechanical systems associated with the measuring and transmission to the surface of the data. As the drilling process proceeds the drill bit will rise and fall with rotation. This is one of several factors which can cause the bit load to vary, further causing the bit to produce irregular demands on power, thus rendering the drill bit as a cause of drill strings vibrations. Additionally, the rotation of the drill string causes gyrations which are coupled to the drill bit as load and torque variations. Thus, the drill string itself induces irregular power into the bit and thereby causes drill string vibrations. Such vibrations can result in damage to the mechanical and electronic components of the measurement-while-drilling system.
Accordingly, the present invention overcomes these difficulties by providing method and apparatus for reliably securing a measurement-while-drilling-instrument within a drill collar to minimize the potential of damge which could be caused by vibration and/or shock.